Theropods in flight

My vote for the weirdest extant lifeform goes to the Blanket octopuses (Tremoctopus sp.), 4 species of pelagic cephalopod from tropical/subtropical oceans. Females are up to 2 m long and have the characteristic "blankets". Males are tiny (1-2cm long) and have a specially modified right tentacle for sperm storage. During mating, the arm tears itself off and independently wriggles its way inside female, ejecting its load of sperm (hentai tentacle-sex at its finest). Finally, the males and juvenile females rip the stinging tentacles off Portuguese men-of-war for use as hand-held weaponry.

Tuberculate Octopus (Ocythoe tuberculata) is the only cephalopod possessing a true buoyancy-control gas chamber and the only known ovoviviparous cephalopod. Instead of raiding siphonophores for armaments like the blankies, this species turns colonial salps into fortresses.